Carton conveyors are components of high speed continuous motion article packaging machines. Generally, a carton conveyor moves open cartons in a uniformly spaced relationship and in a downstream direction. Articles to be packaged, such as beverage cans or single large beverage containers, are progressively pushed into the open cartons as they are conveyed along, and the cartons are subsequently closed to contain the articles. FIG. 1 illustrates a generic carton conveyor in simplified form for clarity. The carton conveyor 11 essentially comprises a spaced pair of endless chains that move around spaced apart sprockets. More specifically, the conveyor 11 in FIG. 1 has an upper carton flight 12 that moves in a downstream direction 17 and a lower flight 13 that returns in the opposite direction. The flights travel around an upstream sprocket 19 and a downstream sprocket 18. Trailing flight lugs 14 and leading flight lugs 15 are attached to and are carried along with the chains of the conveyor. The pairs of flight lugs are spaced along the chains to separate, contain, and confine cartons 16 of a specific size and to convey the cartons 16 in the downstream direction 17 for being loaded with articles. In some cases, the cartons 16 are pre-erected by a carton erector and delivered to the upper flight 12, as indicated schematically on the left in FIG. 1. Those of skill in the art will understand that carton conveyors of packaging machines are significantly more complex than illustrated in FIG. 1. A more detailed example is disclosed in U.S. Pat. No. 5,234,314, owned by the assignee of the present invention, the contents of which are hereby incorporated fully by reference.
There is a market demand for articles packaged in octagonal cartons; that is, cartons having eight sides. Erecting octagonal cartons, delivering them to a carton conveyor, and maintaining their shape accurately as they move downstream along the carton conveyor presents unique challenges. A need exists for a method and apparatus that will erect octagonal cartons accurately and consistently and hold them in shape for receiving articles to be packaged as they move downstream along the upper or carton flight of a carton conveyor. More broadly, a need exist for a method and apparatus for erecting and conveying non-rectangular cartons along a carton flight. It is to the provision of such a method and apparatus that the present invention is primarily directed.